Spatial repositioning of multiple audio streams

ABSTRACT

An audio rendering system includes a processor that combines audio input signals with personalized spatial audio transfer functions preferably including room responses. The personalized spatial audio transfer functions are selected from a database having a plurality of candidate transfer function datasets derived from in-ear microphone measurements for a plurality of individuals. Alternatively, the personalized transfer function datasets are derived from actual in-ear measurements of the listener. Foreground and background positions are designated and matched with transfer function pairs from the selected dataset for the foreground and background direction and distance. Two channels of input audio such as voice and music are processed. When a voice communication such as a phone call is accepted the music being rendered is moved from a foreground to a background channel corresponding to a background spatial audio position using the personalized transfer functions. The voice call is simultaneously transferred to the foreground channel.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/216,561, filed Mar. 29, 2021, and titled, “SPATIAL REPOSITIONING OFMULTIPLE AUDIO STREAMS.” Which is is a continuation-in-part of U.S.patent application Ser. No. 16/213,979, filed Dec. 7, 2018, and titled,“SPATIAL REPOSITIONING OF MULTIPLE AUDIO STREAMS.” This applicationincorporates by reference in their entirety to the disclosures from U.S.Patent Application Ser. No. 62/614,482, filed Jan. 7, 2018, and titled,“METHOD FOR GENERATING CUSTOMIZED SPATIAL AUDIO WITH HEAD TRACKING”;International Application No. PCT/SG2016/050621, filed Dec. 28, 2016 andentitled “A METHOD FOR GENERATING A CUSTOMIZED/PERSONALIZED HEAD RELATEDTRANSFER FUNCTION”, which claims the benefit of priority from SingaporePatent Application No. 10201510822Y, filed Dec. 31, 2015 and entitled “AMETHOD FOR GENERATING A CUSTOMIZED/PERSONALIZED HEAD RELATED TRANSFERFUNCTION”, the entirety of which are incorporated by reference for allpurposes. This application further incorporates by reference in theirentirety the disclosures from U.S. patent application Ser. No.15/969,767 filed on May 2, 2018 and titled “SYSTEM AND A PROCESSINGMETHOD FOR CUSTOMIZING AUDIO EXPERIENCE”; and U.S. patent applicationSer. No. 16/136,211 filed on Sep. 19, 2018, and titled “METHOD FORGENERATING CUSTOMIZED SPATIAL AUDIO WITH HEAD TRACKING.”

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to methods and systems for generatingaudio for rendering over headphones. More particularly, the presentinvention relates to using databases of personalized spatial audiotransfer functions having room impulse response information associatedwith spatial audio positions together with audio streams and generatingspatial audio positions using the personalized spatial audio transferfunctions to create more realistic audio rendering over headphones.

2. Description of the Related Art

Often a user is listening to music on his phone when a phone call comesin and may wish the music to continue uninterrupted. Unfortunately, mostphones are configured to mute the music when the call is accepted. Whatis needed is an improved system that allows the music or other audio tocontinue uninterrupted when the call is accepted and also allows forallowing the user to distinguish between the two different audiosources.

SUMMARY OF THE INVENTION

To achieve the foregoing, the present invention provides in variousembodiments a processor and system configured to provide binauralsignals to headphones, the system including means for placing audio in afirst input audio channel in a first position, such as a foregroundposition, and means for placing audio in a second input audio channel ina second position, such as a background position.

In some of the embodiments of the present invention, the system includesdatabases of personalized spatial audio transfer functions having roomimpulse response information (such as HRTFs or BRIRs) associated withspatial audio positions together with at least two audio streams.Together the personalized BRIRs for at least two locations are used withthe two input audio streams to establish a foreground spatial audiosource and a background spatial audio source to provide an immersiveexperience for the listener through headphones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating spatial audio positions for audioprocessed in accordance with some embodiments of the present invention.

FIG. 2 is a diagram illustrating a system for presenting an audio sourcesuch as from any of several different types of media and a voicecommunication at different spatial audio locations in accordance withsome embodiments of the present invention.

FIG. 3 is a diagram illustrating a system for generating BRIRs forcustomization, acquiring listener properties for customization,selecting customized BRIRs for listeners, and for rendering audiomodified by BRIRs in accordance with embodiments of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to preferred embodiments of theinvention. Examples of the preferred embodiments are illustrated in theaccompanying drawings. While the invention will be described inconjunction with these preferred embodiments, it will be understood thatit is not intended to limit the invention to such preferred embodiments.On the contrary, it is intended to cover alternatives, modifications,and equivalents as may be included within the spirit and scope of theinvention as defined by the appended claims. In the followingdescription, numerous specific details are set forth in order to providea thorough understanding of the present invention. The present inventionmay be practiced without some or all of these specific details. In otherinstances, well known mechanisms have not been described in detail inorder not to unnecessarily obscure the present invention.

It should be noted herein that throughout the various drawings likenumerals refer to like parts. The various drawings illustrated anddescribed herein are used to illustrate various features of theinvention. To the extent that a particular feature is illustrated in onedrawing and not another, except where otherwise indicated or where thestructure inherently prohibits incorporation of the feature, it is to beunderstood that those features may be adapted to be included in theembodiments represented in the other figures, as if they were fullyillustrated in those figures. Unless otherwise indicated, the drawingsare not necessarily to scale. Any dimensions provided on the drawingsare not intended to be limiting as to the scope of the invention butmerely illustrative.

Binaural technology, which generally refers to technology relating to orused with both ears, enables the user to perceive audio in athree-dimensional field. This is accomplished in some embodimentsthrough the determination and use of the Binaural Room Impulse Response(BRIR) and its related Binaural Room Transfer Function (BRTF). The BRIRsimulates the interaction of sound waves from a loudspeaker with thelistener's ears, head and torso, as well as with the walls and otherobjects in the room. Alternatively, the Head Related Transfer Function(HRTF) is used in some embodiments. The HRTF is a transfer function inthe frequency domain corresponding to the impulse responses representingthe interactions in an anechoic environment. That is, the impulseresponses here represent the sound interactions with listener ears, headand torso.

According to known methods for determining HRTFs or BRTFs, a real ordummy head and binaural microphones are used to record a stereo impulseresponse (IR) for each of a number of loudspeaker positions in a realroom. That is, a pair of impulse responses, one for each ear, isgenerated for each position. This pair is referred to as the BRIR. Amusic track or other audio stream may then be convolved (filtered) usingthese BRIRs and the results mixed together and played over headphones.If the correct equalization is applied, the channels of the music willthen sound as if they were being played in the speaker positions in theroom where the BRIRs were recorded.

Often a user is listening to music on his phone when a phone call comesin and the user may wish the music to continue uninterrupted when thecall is accepted. Rather than invoking a mute function, the two separateaudio signals, i.e., the phone call and the music, can be fed into thesame channel(s). But generally, humans have difficulty distinguishingsound sources that come from the same direction. To solve this problem,and in accordance with one embodiment, when an incoming call comes in,the music is directed from a first position to a speaker or channel in asecond position such as a background position, i.e., the music and voicecommunication are placed in different positions. Unfortunately, whilethese methods of positioning rendered audio streams when used withmulti-speaker setups allow separation of the sources, a large percentageof voice communications today come in over mobile phones, which are notusually connected to multichannel speaker setups. Furthermore, even suchmethods used with multichannel setups sometimes provide a less thanoptimal result when the audio sources are designated by panning forpositions that are not completely aligned with the physical positions ofthe loudspeakers. This is due in part to the difficulties for listenersin precisely localizing spatial audio positions when such positions areapproximated by traditional panning methods to move the perceived audioposition to a location between multichannel speaker positions.

The present invention solves these problems of voice communication overheadphones by automatically positioning the voice call and the music indifferent spatial audio positions by using positions virtualized usingtransfer functions that at least simulate the effects from at least anindividual's head, torso, and ears on the audio such as by using HRTFs.More preferably, room effects on the audio are considered by processingthe audio streams with BRIRs. But commercially available BRIR datasetsthat are non-individualized give most users a poor sense ofdirectionality and an even poorer sense of distance of the perceivedsound sources. This might cause difficulty in distinguishing soundsources.

To solve these additional issues, the present invention in someembodiments uses individualized BRIRs. In one embodiment, the generationof individualized HRTF or BRIR datasets are generated by insertingmicrophones in the listener's ears and recording the impulse responsesin a recording session. This is a time-consuming process that may beinconvenient for inclusion in the sale of mobile phones or other audiounits. In further embodiments, the voice and music sound sources arelocalized at separate first (e.g, foreground) and second (e.g.background) locations using individualized BRIRs (or associated BRTFs)derived from the extraction of image-based properties for eachindividual listener, said properties used to determine a suitableindividualized BRIR from a database having a candidate pool ofindividualized spatial audio transfer functions for a plurality ofmeasured individuals. The individualized BRIRs corresponding to each ofthe at least two separate spatial audio positions is preferably used todirect a first and second audio stream to two different spatial audiopositions.

Further still, since it is known that humans are better able todistinguish two sound sources when one is determined by the listener tobe closer and another is determined to be farther away, in someembodiments the music is automatically placed at a distance in thebackground spatial position and the voice is placed at a nearer distanceusing individualized BRIRs derived using the extracted image-basedproperties.

In one further embodiment, the extracted image-based properties aregenerated by the mobile phone. In another embodiment, upon determinationthat the voice call is of a lower priority, the voice call is directedfrom the foreground to the background and the music to the foregroundupon receipt of a control signal from the listener, such as generated byactivating a switch. In yet another embodiment, upon determination thatthe voice call is of a lower priority and upon receipt of a controlsignal from the listener, the apparent distance of the voice call isincreased and the apparent distance of the music is decreased usingindividualized BRIRs corresponding to different distances for the samedirections.

While it should be understood that most of the embodiments hereindescribe the personalized BRIRs in use with headphones, the techniquesfor positioning media streams in conjunction with voice communicationsdescribed can also be extended to any suitable transfer functionscustomized for the user in accordance with the steps described withrespect to FIG. 3 .

It should be understood that the scope of the present invention isintended to cover placing the respective first audio source and thevoice communication at any position around the user. Further, the useherein of foreground and background is not intended to be limited torespectively areas in front of the listener or behind the listener.Rather, foreground is to be interpreted in its most general sense asreferring to the more prominent or important of the two separatepositions and in turn background referring to the less prominent of theseparate positions. Further still, it should be noted that the scope ofthe present invention occurs in the very general sense directing thefirst audio stream to a first location and the second audio stream to asecond spatial audio position using the HRTFs or BRIRs in accordancewith the techniques described herein. It should be further noted thatsome embodiments of the invention can extend to the selection of anydirectional location around the user for either of the foreground orbackground positions with the simultaneous application of attenuation ofsignals in lieu of assigning a closer distance to the foregroundposition and a farther distance to a background position. In itssimplest form, filtering circuitry applying two pairs of BRIRs torepresent foreground and background positions will be initially shown inaccordance with embodiments of the present invention.

FIG. 1 is a diagram illustrating spatial audio positions for audioprocessed in accordance with some embodiments of the present invention.Initially a listener 105 may be listening through headphones 103 to afirst audio signal such as music. Using BRIRs applied to the first audiostream the listener senses that the first audio stream is coming from afirst audio position 102. In some embodiments this is a foregroundposition. One technique, in one embodiment, places this foregroundposition at the zero-degree position relative to the listener 105. Whena triggering event occurs, such as in one embodiment the receipt of aphone call, the second stream (e.g., the voice communication or phonecall) is routed to the first position (102) while the first audio signalis routed to a second position 104. In the example embodiment shown,this second position is placed at the 200-degree position, which in someembodiments is described as a less prominent or background position. The200-degree position is selected only as a non-limiting example.Placement of the audio stream at this second position is achievedpreferably using BRIRs (or BRTFs) that correspond to the azimuth,elevation, and distance for this second position for the listener ofinterest.

In one embodiment, the transition of the first audio stream to thesecond position (e.g., background) occurs abruptly without providing anysense that the first audio stream is moving through intermediate spatialpositions. This is depicted graphically by path 110, which shows nointermediate spatial positions. In another embodiment, the audio ispositioned at intermediate points 112 and 114 for short transitory timeperiods to provide the sense of movement directly or alternatively in anarc from the foreground position 102 to background position 104. In apreferred embodiment BRIRs for the intermediate positions 112 and 114are used to spatially position the audio streams. In alternativeembodiments, the sense of movement is achieved by using BRIRs for theforeground and background positions and panning between those virtualloudspeakers corresponding to those foreground and background positions.In some embodiments, the user may recognize that the voice communication(e.g., phone call) is not deserving of priority status and choose torelegate the phone call to a second position (e.g. a backgroundposition) or even to a user selected third position and the music backto a first (e.g., foreground) position. In one embodiment this isperformed by sending the audio stream corresponding to music back to theforeground (first) position 102 and sending the voice communication tothe background position 104. In another embodiment this reranking ofpriorities is performed by making the voice call more distant and themusic closer to the listener head 105. This is preferably done byassigning a new HRTF or BRTF for the listener captured at differentdistances, calculated or interpolated from the captured measurements torepresent the new distances. For example, in order to increase thepriority of the music from background position 104, the apparentdistance may be decreased to either spatial audio position 118 or 116.This reduced distance, accomplished preferably by processing the musicaudio stream with new HRTFs or BRTFs increases the volume of the musicin relation to the voice communication signal. The voice signal maysimultaneously in some embodiments be increased in distance from thelistener head 105, again either from the selection of captured HRTF/BRTFvalues or interpolated. The interpolation/calculation may be done usingmore than 2 points. For example, to get a point which is an intersectionof two lines (AB and CD), the interpolation/calculation may require thepoints A, B, C, and D.

Alternatively, the spatial audio position generating the voicecommunication may be maintained at a stationary position during thereranking steps or increased. In some embodiments, the two separateaudio streams enjoy equal prominence.

In yet other embodiments, the user can choose from a user interfacespatial audio positions for at least one of the streams, morepreferably, single or multiple locations for all of the streams.

FIG. 2 is a diagram illustrating a system for simulating an audio sourceand a voice communication at different spatial audio locations inaccordance with some embodiments of the present invention. FIG. 2depicts generally two different streams (202 and 204) entering thespatial audio positioning system by using separate pairs of filters(i.e., filters 207,208) for a first spatial audio position and filters209, 210 for a second spatial audio position. Gain 222-225 may beapplied to all of the filtered streams before the signals respectivelyfor the left headphone cup are added on adder 214 and the filteredresults for the right headphone cup of headphone 216 are similarly addedin adder 215. While this collection of hardware modules shows the basicprincipals involved, other embodiments use BRRIs or HRTFs stored inmemory such as memory 732 of audio rendering module 730 (such as amobile phone) as illustrated in FIG. 3 . In some embodiments thelistener is aided in discerning between the first and second spatialaudio positions by the fact that those spatial audio positions aregenerated by selecting transfer functions having room responses inaddition to the HRTFs for the individuals. In preferred embodiments, thefirst and second positions are determined using BRIRs customized for thelistener.

The systems and methods for rendering over headphones work best when theHRTF or BRTF is individualized for the listener by either direct in-earmicrophone measurement or alternatively individualized BRIR/HRIRdatasets where in-ear microphone measurements are not used. Inaccordance with preferred embodiments of the present invention, onecustom method for generating the BRIRs is used which involves theextraction of image-based properties from a user and determining asuitable BRIR from a candidate pool of BRIRs as depicted generally byFIG. 3 . In further detail, FIG. 3 illustrates a system for generatingHRTFs for customization use, acquiring listener properties forcustomization, selecting customized HRTFs for listeners, providingrotation filters adapted to work with relative user head movement andfor rendering audio as modified by BRIRs in accordance with embodimentsof the present invention. Extraction Device 702 is a device configuredto identify and extract audio related physical properties of thelistener. Although block 702 can be configured to directly measure thoseproperties (for example the height of the ear) in preferred embodimentsthe pertinent measurements are extracted from images taken of the user,to include at least the user's ear or ears. The processing necessary toextract those properties preferably occurs in the Extraction Device 702but could be located elsewhere as well. For a non-limiting example, theproperties could be extracted by a processor in remote server 710 afterreceipt of the images from image sensor 704.

In a preferred embodiment, image sensor 704 acquires the image of theuser's ear and processor 706 is configured to extract the pertinentproperties for the user and sends them to remote server 710. Forexample, in one embodiment, an Active Shape Model can be used toidentify landmarks in the ear pinnae image and to use those landmarksand their geometric relationships and linear distances to identifyproperties about the user that are relevant to generating a customizedBRIR from a collection of stored BRIR datasets, that is, from acandidate pool of BRIR datasets. In other embodiments an RGT model(Regression Tree Model) is used to extract properties. In still otherembodiments, machine learning such as neural networks and other forms ofartificial intelligence (AI) are used to extract properties. One exampleof a neural network is the Convolutional neural network. A fulldiscussion of several methods for identifying unique physical propertiesof the new listener is described in Application PCT/SG2016/050621, filedon Dec. 28, 2016 and titled “A Method for Generating a customizedPersonalized Head Related Transfer Function”, which disclosure isincorporated fully by reference herein.

The remote server 710 is preferably accessible over a network such asthe internet. The remote server preferably includes a selectionprocessor 710 to access memory 714 to determine the best matched BRIRdataset using the physical properties or other image related propertiesextracted in Extraction Device 702. The selection processor 712preferably accesses a memory 714 having a plurality of BRIR datasets.That is, each dataset in the candidate pool will have an BRIR pairpreferably for each point at the appropriate angles in azimuth andelevation and perhaps also head tilt. For example, measurements may betaken at every 3 degrees in azimuth and elevations to generate BRIRdatasets for the sampled individuals making up the candidate pool ofBRIRs.

As discussed earlier, these are preferably derived by measurement within ear microphones on a population of moderate size (i.e., greater than100 individuals) but can work with smaller groups of individuals andstored along with similar image related properties associated with eachBRIR set. These can be generated in part by direct measurement and inpart by interpolation to form a spherical grid of BRIR pairs. Even withthe partially measured/partially interpolated grid, further points notfalling on a grid line can be interpolated once the appropriate azimuthand elevation values are used to identify an appropriate BRIR pair for apoint from the BRIR dataset. For example, any suitable interpolationmethod may be used including but not limited to the adjacent linearinterpolation, bilinear interpolation, and spherical triangularinterpolation, preferably in the frequency domain.

Each of the BRIR Datasets stored in memory 714 in one embodimentincludes at least an entire spherical grid for a listener. In such case,any angle in azimuth (on a horizontal plane around the listener, i.e. atear level) or elevation can be selected for placement of the soundsource. In other embodiments the BRIR Dataset is more limited, in oneinstance limited to the BRIR pairs necessary to generate loudspeakerplacements in a room conforming to a conventional stereo setup (i.e., at+30 degrees and −30 degrees relative to the straight ahead zero positionor, in another subset of a complete spherical grid, speaker placementsfor multichannel setups without limitation such as 5.1 systems or 7.1systems.

The HRIR is the head-related impulse response. It completely describesthe propagation of sound from the source to the receiver in the timedomain under anechoic conditions. Most of the information it containsrelates to the physiology and anthropometry of the person beingmeasured. HRTF is the head-related transfer function. It is identical tothe HRIR, except that it is a description in the frequency domain. BRIRis the binaural room impulse response. It is identical to the HRIR,except that it is measured in a room, and hence additionallyincorporates the room response for the specific configuration in whichit was captured. The BRTF is a frequency-domain version of the BRIR. Itshould be understood that in this specification that since BRIRs areeasily transposable with BRTFs and likewise, that HRIRs are easilytransposable with HRTFs, that the invention embodiments are intended tocover those readily transposable steps even though they are notspecifically described here. Thus, for example, when the descriptionrefers to accessing another BRIR dataset it should be understood thataccessing another BRTF is covered.

FIG. 3 further depicts a sample logical relationship for the data storedin memory. The memory is shown including in column 716 BRIR Datasets forseveral individuals (e.g., HRTF DS1A, HRTF DS2A, etc.) These are indexedand accessed by properties associated with each BRIR Dataset, preferablyimage related properties. The associated properties shown in column 715enable matching the new listener properties with the propertiesassociated with the BRIRs measured and stored in columns 716, 717, and718. That is, they act as an index to the candidate pools of BRIRDatasets shown in those columns. Column 717 refers to a stored BRIR atreference position zero and is associated with the remainder of the BRIRDatasets and can be combined with rotation filters for efficient storageand processing when the listener head rotation is monitored andaccommodated. Further description of this option is described in detailin co-pending application Ser. No. 16/136,211, filed Sep. 19, 2018, andtitled, METHOD FOR GENERATING CUSTOMIZED SPATIAL AUDIO WITH HEADTRACKING, which is incorporated fully by reference herein.

In general, one objective of accessing the candidate pool of BRIR (orHRTF) datasets is to generate a customized audio response characteristicfor a person (such as a BRIR dataset). In some embodiments, these areused to process the input audio signals such as the voice communicationand the media streams to position them for the accurate perception ofspatial audio associated with the first position and the secondposition, as described above. In some embodiments, generating thiscustomized audio response characteristic such as the individualizedBRIRs includes extracting image related properties such as biometricdata for the individual. For example, this biometric data can includedata related to the pinna of the ear, the person's ear in general, head,and/or shoulders. In further embodiments, processing strategies such as(1) multiple match; (2) multiple-recognizer types; and (3) cluster basedare used to generate intermediate datasets that are later combined(where multiple hits result) to produce the customized BRIR dataset forthe individual. These can be combined by using weighted sums among othermethods. In some cases there is no need to combine the intermediateresults where there is only a single match. In one embodiment, theintermediate datasets are based at least in part on the closeness of thematch of a retrieved BRIR dataset (from the candidate pool) with respectto extracted properties. In other embodiments multiple recognizermatching steps are used whereby the processor retrieves one or moredatasets based on a plurality of training parameters corresponding tothe biometric data. In still other embodiments, a cluster basedprocessing strategy is used whereby potential datasets are clusteredbased on the extracted data (e.g. biometric data). The clusters comprisemultiple datasets having a relationship where they are clustered orgrouped together to form a model with a corresponding BRIR dataset thatmatches the extracted data (e.g. biometric) from the image.

In some embodiments of the present invention 2 or more distance spheresare stored. This refers to a spherical grid generated for 2 differentdistances from the listener. In one embodiment, one reference positionBRIR is stored and associated for 2 or more different spherical griddistance spheres. In other embodiments each spherical grid will have itsown reference BRIR to use with the applicable rotation filters.Selection processor 712 is used to match the properties in the memory714 with the extracted properties received from Extraction device 702for the new listener. Various methods are used to match the associatedproperties so that correct BRIR Datasets can be derived. As describedabove, these include comparing biometric data by Multiple-match basedprocessing strategy; Multiple recognizer processing strategy; Clusterbased processing strategy and others as described in U.S. patentapplication Ser. No. 15/969,767, titled “SYSTEM AND A PROCESSING METHODFOR CUSTOMIZING AUDIO EXPERIENCE”, and filed on May 2, 2018, whichdisclosure is incorporated fully by reference herein. Column 718 refersto sets of BRIR Datasets for the measured individuals at a seconddistance. That is, this column posts BRIR datasets at a second distancerecorded for the measured individuals. As a further example, the firstBRIR datasets in column 716 may be taken at 1.0 m to 1.5 m whereas theBRIR datasets in column 718 may refer to those datasets measured at 5 m.from the listener. Ideally the BRIR Datasets form a full spherical gridbut the present invention embodiments apply to any and all subsets of afull spherical grid including but not limited to a subset containingBRIR pairs of a conventional stereo set; a 5.1 multichannel setup; a7.1multichannel setup, and all other variations and subsets of a sphericalgrid, including BRIR pairs at every 3 degrees or less both in azimuthand elevation as well as those spherical grids where the density isirregular. For example, this might include a spherical grid where thedensity of the grid points is much greater in a forward position versusthose in the rear of the listener. Moreover, the arrangement of contentin the columns 716 and 718 apply not only to BRIR pairs stored asderived from measurement and interpolation but also to those that arefurther refined by creating BRIR datasets that reflect conversion of theformer to an BRIR containing rotation filters.

After the determination of one or more matching or computed BRIRDatasets, the datasets are transmitted to Audio Rendering Device 730 forstorage of the entire BRIR Dataset determined by matching or othertechniques as described above for the new listener, or, in someembodiments, a subset corresponding to selected spatialized audiolocations. The Audio Rendering Device then selects in one embodiment theBRIR pairs for the azimuth or elevation locations desired and appliesthose to the input audio signal to provide spatialized audio toheadphones 735. In other embodiments the selected BRIR datasets arestored in a separate module coupled to the audio rendering device 730and/or headphones 735. In other embodiments, where only limited storageis available in the rendering device, the rendering device stores onlythe identification of the associated property data that best match thelistener or the identification of the best match BRIR Dataset anddownloads the desired BRIR pair (for a selected azimuth and elevation)in real time from the remote sever 710 as needed. As discussed earlier,these BRIR pairs are preferably derived by measurement with in earmicrophones on a population of moderate size (i.e., greater than 100individuals) and stored along with similar image related propertiesassociated with each BRIR data set. Rather than taking all 7200 points,these can be generated in part by direct measurement and in part byinterpolation to form a spherical grid of BRIR pairs. Even with thepartially measured/partially interpolated grid, further points notfalling on a grid line can be interpolated once the appropriate azimuthand elevation values are used to identify an appropriate BRIR pair for apoint from the BRIR dataset.

Once the custom selected HRTF or BRIR datasets are selected for theindividual, these individualized transfer functions are used to enablethe user or the system to provide at least first and second spatialaudio positions for positioning the respective media stream and voicecommunication. In other words, a pair of transfer functions are used foreach of the first and second spatial audio positions to virtually placethose streams and thereby to enable the listener to focus on hispreferred audio stream (e.g., the phone call or the media stream) due totheir separate spatial audio positions. The scope of the presentinvention is intended to cover all media streams including withoutlimitation audio associated with videos, and music.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

What is claimed is:
 1. A method for distinguishing between a first audiochannel and a second audio channel comprising: associating the firstaudio channel with a first spatial audio position; transitioning betweenthe first spatial audio position and a second spatial audio position byassociating the first audio channel with a first transition path byrendering the first audio channel with a third spatial audio transferfunction that includes an HRF or a Binaural Room Transfer Function(BRTF) corresponding to a third spatial audio position along the firsttransition path; associating the first audio channel with the secondspatial audio position by rendering the first audio channel with asecond spatial audio transfer function that includes an HRF or a BRTFcorresponding to the second spatial audio position; and associating thesecond audio channel with the first spatial audio position after thefirst audio channel vacates its association with the first spatial audioposition, wherein associating the first audio channel with the firstspatial audio position includes rendering the first audio channel with afirst spatial audio transfer function that includes an HRF or a BRTFcorresponding to the first spatial audio position, and whereinassociating the second audio channel with the first spatial audioposition includes rendering the second audio channel with the firstspatial audio transfer function.
 2. The method as recited in claim 1,wherein the first spatial audio transfer function, the second spatialaudio transfer function, and the third spatial audio transfer functionare derived by accessing a database that includes non individualizedHead Related Transfer Functions (HRTFs) or BRTFs.
 3. The method asrecited in claim 1, wherein the first spatial audio transfer functionand the second spatial audio transfer function are derived by accessinga database that includes individualized HRTFs or BRTFs.
 4. The method asrecited in claim 1, wherein the first spatial audio position representsa foreground position and the second spatial audio position represents abackground position.
 5. The method as recited in claim 1, wherein firstspatial audio position represents a foreground position and the secondspatial audio position represents a background position.
 6. The methodas recited in claim 1, wherein transitioning between the first spatialaudio position and the second spatial audio position occurs by using atleast one interim or intermediate position in the transition path byusing an HRTF or BRTF customized for an individual.
 7. The method asrecited in claim 1, wherein the transitioning occurs in an abruptmanner.
 8. The method as recited in claim 1, wherein the first audiochannel and the second audio channel correspond to tracks in a videogame.
 9. The method as recited in claim 1, wherein the first audiochannel corresponds to a media track and the second audio channelcorresponds to a phone call.
 10. The method as recited in claim 1,wherein the receipt of a phone call triggers the transitioning of thefirst audio channel from the first spatial audio position to the secondspatial audio position.
 11. The method as recited in claim 1, furthercomprising receiving a control signal that results in the transition ofthe first audio channel from the second spatial audio position to thefirst spatial audio position.
 12. An audio processing device comprising:a processor configured to render at least a first and a second audiostream at a plurality of spatial audio positions to include at least afirst and second spatial audio position; a memory having a plurality ofspatial audio transfer functions for rendering audio for at least afirst and a second spatial audio position; and a selection processorconfigured to access a database including a plurality of candidatespatial audio transfer function pairs, said pairs accessed and indexedby image based physical properties for a listener and selected ones ofsaid pairs used for positioning the first and second audio streams. 13.The audio processing device as recited in claim 12 wherein the databaseis located remotely from the audio processing device.
 14. The audioprocessing device as recited in claim 12 wherein upon receipt of acontrol signal the processor is configured to move the first audiostream from a foreground position corresponding to the first spatialaudio position to a background position corresponding to the secondspatial audio position and to render the second audio stream into thevacated first spatial audio position.
 15. The audio processing device asrecited in claim 14 wherein the audio processing device is a mobilephone and the control signal is generated by the receipt of a telephonecall.
 16. The audio processing device as recited in claim 15 wherein theprocessor is further configured to attenuate the first audio stream uponreceipt of the phone call.
 17. A method for processing audio streamscomprising: receiving at least two audio streams; assigning each of theat least two audio streams to different ones of spatial audio transferfunctions, wherein each of the spatial audio transfer function arepersonalized for a user and wherein the personalized spatial audiotransfer functions are selected from a database having a plurality ofcandidate transfer function datasets derived from in-ear microphonemeasurements for a plurality of individuals and indexed according toimage based properties; and selecting one of the audio streams to be aforeground stream and one to be a background stream based on theassignment to spatial audio transfer functions.
 18. The method asrecited in claim 17 wherein the spatial audio transfer functionscomprise HRTFs or BRTFs and the at least two audio streams are renderedover headphones.